With the advancements in manufacturing technologies and miniaturization of electronics packaging, the military and commercial industry has enjoyed many advantages over the past 15 to 20 years using electronic and microelectronics design and packaging techniques. The use of microelectronics packaging techniques has allowed military and other users to increase their system complexities and hardware performance, but at the same time, reduce their size and weight requirements. This packaging trend is unlikely to stop and the miniaturization technology undoubtedly will continue.
As manufacturing techniques for microelectronics assemblies advance, hardware density and complexity are pushed to practical limits. Production yields and hardware reliability are heavily dependent on the dimensional, positional and attachment feedback throughout the manufacturing process. The lack of real-time, high resolution, non-contact sensors dictates that quality assurance check points have to be placed at the end of manufacturing cycles and processes, so that actual quality of the hardware produced can be verified or inspected.
Industry responded to the above challenge by developing and implementing automated manufacturing and inspection machines to minimize quality assurance costs with more consistent results. Though with some significant accomplishments, there are many challenges ahead. For example quality standards such as Mil-Std-883, Mil-H-38534 and others were designed and written specifically to govern the universal manufacturing quality of microelectronics and electronic hardware. Most of these quality standards require visual verification of the dimension, shape, physical configuration as well as appearance of the part under test. Due to the size, complexity and fragility of the materials used, these quality standards cannot always be accurately measured or pin-pointed by a human operator or existing sensors. Nor can they be sensed during the manufacturing cycle to support real-time feed back loops for process control.
As an example, one pass/fail criteria concerns attachment or bonding integrity of features such as ball bonds, wedge bonds or solder joints. The existence of balls, wedges and other conductor bonds might be detectable by machine vision sensors with acceptable speed and resolution for process control. However, the integrity of such bonds cannot in any practical sense be evaluated or analyzed by visual inspection means. Microcircuit bonding quality checks today are generally performed using bond pull and bond shear techniques and machines. The bond shear test is a destructive test which cannot be used on functional bonds. The bond pull test requires a controlled pull force to ensure no damaging effect on the bond wires. Both of these approaches require the use of contact type sensors which are slow, labor intensive and above all, change the original configuration of the bond wires being tested. In addition, these techniques cannot be used to support real-time process control on high speed manufacturing tasks.
Further while these techniques may have been acceptable in past years, they are not capable of keeping up with the rest of today's and future high speed manufacturing processes. Additionally, visual inspection is not a most effective technique for detecting delamination between material layers or attachment integrity of bonding materials, such as ball bonds, trace attachments, etc. The above labor intensive inspection efforts and human judgment calls are major contributors to the "cost of quality" of electronic products today.
It would be desirable to develop automated, non-contacting methods and equipment for evaluating the integrity of electronic, and even more specifically microelectronic, conductor bonds to substrates, such as to electronic and microelectronic integrated circuitry formed within a semiconductor substrate, as well as soldering joints or other conductor bonds. This invention spawned out of needs and concerns associated with the electronics and microelectronics industry, and specifically to the evaluation of ball bonds and wedge bonds in the microelectronics industries. However, the artisan will appreciate that the invention may have utility in evaluating integrity of other conductor bonds.